Fix EM102: extract exception f-strings into variables

[Copilot]

Ruff rule EM102 prohibits f-string literals as direct exception arguments (they bloat tracebacks). This removes EM102 from the pyproject.toml suppression list and fixes all 42 violations across 14 files.

Pattern applied

# Before
raise ValueError(f"No such reusable taskflow: {task.uses}")

# After
msg = f"No such reusable taskflow: {task.uses}"
raise ValueError(msg)

Files changed

• pyproject.toml — removed EM102 from [tool.ruff.lint] ignore
• agent.py, available_tools.py, cli.py, mcp_lifecycle.py, mcp_transport.py, mcp_utils.py, models.py, runner.py, session.py, shell_utils.py, template_utils.py — first-party fixes
• mcp_servers/codeql/client.py, mcp_servers/codeql/mcp_server.py, mcp_servers/codeql/jsonrpyc/__init__.py — MCP server fixes

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• unsupported.example.com
  • Triggering command: /usr/bin/python python -m pytest tests/ -x -q (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)